Linear actuators that employ voice coil motors in order to move lenses and the like with good response are widely employed for the purpose of carrying out focusing or the like. In a magnetic drive linear actuator, a mover is supported by a linear guide or the like so as to be capable of linear movement, and a support for attaching a lens or other element to be driven is fastened to the mover.
Typically, a requirement of a magnetic drive linear actuator is the ability to cause a lens or other such load to perform linear movement within a very small range, at good responsiveness and high accuracy of positioning. In Patent Document 1, the inventors of the present invention proposed a magnetic drive linear actuator with the aim of improving the accuracy of positioning and improving durability.
This linear actuator has a rectangular tubular coil frame, inside which are arranged a load attachment portion, a linear guide, and a sensor portion for detecting the position of the mover, with the center of gravity of the mover and the center of support of the linear guide being aligned. Also, the center of generation of magnetic force (thrust force) acting on the mover is aligned with the center of gravity of the mover. In so doing, a moment bearing on a section of the linear guide can be reduced, and the mover can be positioned at good responsiveness and high accuracy of positioning. Also, a moment acting on the linear guide which supports the mover is reduced, whereby the durability of the linear actuator can be improved.
Patent Document 1: JP 2008-35645 A